25 March 2015

On the JOIDES Resolution: Turbidite Transport (+ video)

Posted by nbompey

By Diane Hanano

This is the latest in a series of dispatches from education officers aboard the JOIDES Resolution, a scientific ocean drilling ship currently on a two-month research expedition in the Bay of Bengal. Read more posts here.

A submarine canyon -- a big indention in the seafloor -- transports sediments from the near-shore to deeper water. Sediment from the Himalaya mountains is ultimately deposited in the Bengal Fan, where scientists aboard the JOIDES Resolution drill sediment cores to study the mountain range and past climates.  Credit: Lisa Strong

A submarine canyon — a big indention in the seafloor — transports sediments from the near-shore to deeper water. Sediment from the Himalaya mountains is ultimately deposited in the Bengal Fan, where scientists aboard the JOIDES Resolution drill sediment cores to study the mountain range and past climates.
Credit: Lisa Strong

As someone who is used to studying ocean island basalt, I have to admit that I never paid much attention to sediments before.  But now, as an Education Officer for IODP Expedition 354 drilling into the Bengal submarine fan, all of that has changed.  Every 90 minutes or so, we hear the announcement “core on deck,” and another ~10 meters (33 feet) of sediments appear from the bottom of the ocean.

On this expedition, we’re studying sediments that have been eroded from the Himalayas, the highest mountain range in the world.  The Ganges and Brahmaputra rivers carry this sediment to the delta in Bangladesh, but what happens next?  How does this material get all the way out to the middle of the Bay of Bengal where we’re drilling, almost 2,000 kilometers (1,243 miles) away?

Evidence shows up when we split open our cores.  We see repeated sequences of sedimentary deposits called turbidites.  These deposits are formed when a fast-moving sediment-laden current of water (kind of like an underwater avalanche) loses energy and drops its sediment on the seafloor.

To help illustrate this important sediment transport mechanism, a scientist and a technician on board spent part of their rare free moments and built a small tank to generate turbidity currents. We stuck a GoPro into it and used some footage in our new 4.5-minute video “Turbidite Transport.”

– Diane Hanano is the scientific coordinator for IODP-Canada and an education officer aboard the JOIDES Resolution.